Loop taker for sewing machines



July 2, 1968 s. J. KETTERER LOOP TAKER FOR SEWING MACHINES 5 Sheets-Sheet 1 Filed Au 29, 1966 I} INVENTOR. Stcirjlei J; Ketterer July 2, 1968 5. J. KETTERER LOOP TAKER FOR SEWING MACHINES 5 Sheets-Sheet 2 Filed Aug. 29, 1966 lNVENTOR. Stanley J. Kefierer BY 2 ATZJBNEY 4 an F July 2, 1968 I s. J. KETTERER' 3,390,653

LOOP TAKER FOR SEWING MACHINES Filed Aug. 29, 1966 3 Sheets-Sheet 3 INVENTOR. Stanley J. Keiterer -A ORNEY WITNESS:

United States Patent ()1 :"fice 3,39%,653 Patented July 2, 1968 3,390,653 LOOP TAKER FOR SEWING MACHINES Stanley J. Ketterer, Morris Plains, N..l., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Aug. 29, 1966, Ser. No. 575,629 8 Claims. 11. 112-228) ABSTRACT OF THE DESCLOSURE A rotary hook for a lockstitch sewing machine is disclosed in which the bobbin case restraining means is arranged internally of the rotary hook and in which the bobbin case is journaled in a raceway in the rotary hook provided in part by a detachable split ring which may be snapped into the hook body and extends radially over the bobbin case.

This invention relates to loop takers for sewing machines, and more particularly, to a novel lock stitch rotary loop taker of the type referred to in the art as a rotary hook.

It is an object of this invention to provide a rotary hook construction which is advantageously economical to manufacture and easy to assemble.

Another object of this invention is to provide a rotary hook construction which is suitable for use either on zigzag sewing or straight stitching, and more particularly can provide when zigzag stitching for optimum balance in the direction of bobbin thread lead to the left or right hand stitches of a zigzag pattern; and when straight stitching can provide for a bobbin thread lead uniformly from that side which minimizes half hitching.

Still another object of this invention is to provide a novel means associated with the loop taker metering the bobbin thread during stitch formation. More particularly, this invention provides in a vertical axis rotary hook a novel bobbin thread pull-off fin arrangement. Because of the unique combination with the bobbin case rotation restraint internally of the rotary hook body, the pull-off fin can be advantageously arranged closely adjacent to and above the bobbin case in a plane perpendicular to the axis of turning movement of the loop taker body. With this arrangement, the vertical axis hook may be located with minimum spacing beneath the work support advantageously minimizing the needle stroke and minimizing the length of needle thread which must be manipulated during stitch formation.

In the accompanying drawings, a preferred embodiment of this invention is illustrated in which:

FIG. 1 represents a top plan view of the loop taker of this invention and including only a fragment of the sewing machine frame,

FIG. 2 is a vertical cross sectional view of the loop taker taken substantially along line 22 of FIG. 1 and illustrating the arrangement of the loop taker in the sewing machine frame,

FIG. 3 is a vertical cross sectional view of a fragment of the bobbin case of the loop taker together with the rotation restraining finger taken substantially along line 3-3 of FIG. 1,

FIG. 4 is an exploded perspective view of the loop taker,

FIGS. 5, 6, and 7 are top plan views of the loop taker in various successive positions of rotation during needle thread manipulation in the formation of a lock stitch, and

FIG. 6A is an elevational view of a fragment of the bobbin case and rotation restraining finger with the sewing threads shown in position corresponding to that occupied in FIG. 6 and including a representation of work fabric being stitched.

In FIG. 2 of the drawings, the loop taker of this invention, which is indicated generally as 11, is illustrated as it is carried in a sewing machine work supporting bed 12. The bed 12 is formed with depending flanges 13 defining a loop taker cavity 14 partially closed at the bottom by a web 15 in which the loop taker is journaled. At the top, a portion of the loop taker cavity is bridged by a throat plate 16 which is slotted to accommodate a conventional work feed dog 17 and also formed with a needle aperture 18 through which a thread carrying needle 19 reciprocates to cooperate with the loop taker in the formation of lock stitches.

Journaled in a bushing 21 in a flange 13 of the bed is a rotary bed shaft 22 which extends into the loop taker cavity 14 and has fixed thereon as by a set screw 23 a loop taker driving bevel gear 24.

The loop taker 11 is journaled for turning movement about a substantially vertical axis in a bushing 25 carried in the web 15 of the Work supporting bed. Journaled in the bushing 25 is a loop taker shaft 26 formed with an axial bore 27 and at the top with a shouldered flange 28. Fixed to the loop taker shaft directly beneath the flange 28 as by a set screw 29 is a bevel gear 30 which meshes with the loop taker driving bevel gear 24.

The flange 28 of the loop taker shaft 26 has secured to it by screws 31 a cup-shaped upwardly open loop taker body portion 32. The loop taker body portion may be formed as a sheet metal stamping and includes a flat bottom portion 33 and a straight cylindrical sidewall 34. The bottom portion 33 is apertured at at 35 to embrace the shoulder of the flange 28 on the loop taker shaft. The cylindrical sidewall 34 of the loop taker body portion is formed with a plurality of spaced inwardly extending lugs 36 which are preferably struck inwardly from the sidewall each at the same distance axially of the loop taker body portion from the bottom portion 33. The lugs 36 collectively define an inner or lower bearing race for a bobbin case 37 which will be described in detail hereinbelow. The cylindrical sidewall 34 of the loop taker body portion is also formed with a trapezoidal notch 38 of which one acute angular portion defines a throat 39 into which thread loops seized by the loop taker are drawn after loop seizure.

Seated upon the rim of the cylindrical sidewall 34 is an annular loop taker beak ring 41 which as illustrated in FIG. 2 is formed with an L-shaped cross section including a vertical limb 42 depending inside the cylindrical sidewall 34 of the loop taker body portion, and a horizontal limb 43 overlying the rim of the cylindrical sidewall 34 of the loop taker body. The loop taker beak ring 41 is formed with a gap 44 and at one side of the gap the horizontal limb 43 is formed with a needle thread engaging beak 45. Substantially diametrically opposite the beak 45, the horizontal limb 43 is also formed with an inwardly extending thread camming fin 46 which thus extends perpendicular to the axis of the loop taker body.

Because of the gap 44 in the loop taker beak ring it may be formed or sprung into a nominal diameter larger than that of the cylindrical sidewall of the loop taker body portion and pressed into a smaller overall diameter during insertion of the vertical limb 42 into the loop taker body portion. When the beak ring thus assembled is released, the vertical limb 42 will be urged outwardly tightly against the cylindrical sidewall 34. While this frictional engagement may be sufficient to lock the back ring in place on the loop taker body portion locking pins 47 into the cylindrical sidewall 34 and into apertures 48 in the beak ring may be used positively to interlock the beak ring in place on the loop taker body portion with the gap 44 overlying the trapezoidal notch 38. The horizontal limb 43 of the loop taker beak ring is formed adjacent to the beak 45 with an outwardly extending shoulder 49 which serves as a thread stop to prevent a needle thread loop which is seized by the beak from slipping downwardly over the loop taker body portion.

The vertical limb 42 of the beak ring extends in spaced relation to the lugs 36 struck into the loop taker body portion and complements the lugs in providing an upper bearing surface constraining the bobbin case 37 rotatably within the loop taker body portion.

The bobbin case 37 is preferably formed of a moulded synthetic plastic material and is formed with a substantially cylindrical center portion 51 including an internal cylindrical bobbin accommodating cavity 52 of which the bottom wall is formed with an aperture 53. Extending outwardly from the central cylindrical portion of the bobbin case is an annular bearing rib 54 which is formed with a gap 55 defining at one side a substantially radially extending shoulder 56 adapted, as will be described in greater detail hereinbelow, to intercept and separate two limbs of a needle thread loop seized by the loop taker beak during sewing. The upper surface of the bearing rib of the bobbin case is formed with spaced recesses 57, 58 one on each side of a land portion 59 which land portion is disposed midway opposite the gap 55 in the bearing rib. Spanning both recesses 57, 58 as well as the land portion 59 is a fiat leaf spring 60 which is semi-circular in configuration generally conforming to the shape of and overlying the bearing rib. A fastening screw 61 secures the spring upon the bearing rib while a tension adjusting screw 62 threaded through the spring bears against the bearing rib in the recess 58, and serves to regulate the force with which the spring is biased against the land portion 59 thus to regulate the friction which will be applied by the spring to resist passage of thread between the spring and the land portion. The spring is formed above the land portion 59 with a thread guiding notch 63 and adjacent to the notch 63 with an outwardly projecting finger 64 which enters a slot 65 in an upturned needle guarding lip 66 formed on the bobbin case to extend across the gap. Near the free extremity of the spring 60 a thread engaging car 67 is for-med to extend radially outward from the spring and the free extremity of the spring beyond the ear is slightly upturned as at 68 for the purpose of facilitating the manual insertion of bobbin thread under the spring. The cylindrical portion 51 of the bobbin case may be formed with a notch 72 which facilitates access to the bobbin cavity 52 for removal of a bobbin thereon.

The central cylindrical portion 51 of the bobbin case 37 i formed beneath the land portion 59 with a rotation restraining notch 75 which, as illustrated in FIG. 3, embraces an upstanding rotation restraining finger 76 formed on a plate 77 occupying a position beneath the bobbin case within the loop taker body portion 32. The plate 77 is secured to or formed integrally with a rod 78 which is journaled in the bore 27 of the loop taker shaft 26 and beneath the loop taker shaft has a control arm secured thereto as by a set screw 79. An upstanding pin 81 fixed in the control arm passes with clearance upwardly through a slot 82 in the sewing machine bed web 15 in the loop taker accommodating cavity 14 and serves as a handle accessible to the machine operator to vary, within limits, the angular position of bobbin case restraint. A detent pin 83 in the control arm biased upwardly by a leaf spring 84 secured to the control arm by a screw 85 and engageable selectively with notches 86, 87 beneath the web 15 may be used to define selected positions of adjustment of the angular position of bobbin case restraint. Referring to FIG. 1, the web 15 adjacent to the slot 82 may be provided with indicia 88 making easily recognizable the possible selected positions of bobbin case rotation restraint as, for instance, for straight stitching or for zigzag sewing.

The bobbin, which is indicated generally at 90 and is best illustrated in FIG. 4, may be of conventional configuration including a central hub portion 91 and identical spaced flanges 92. Preferably, the outside surfaces of each of the flanges 92 is rounded as at 93 to facilitate passage of needle thread loops across the bobbin during sewing. The bobbin may be placed in the bobbin accommodating cavity 52 of the bobbin case with either flange 92 uppermost. The bobbin thread tensioning spring 60 is threaded by directing bobbin thread into a notch 94 along the rim of the central cylindrical sidewall 34 of the bobbin case from which the bobbin thread can be drawn underneath the free extremity 68 of the spring 60. By drawing the thread beneath the spring 60, the thread can be led into a thread guide slot 95 in the cylindrical sidewall 51 thence between the spring 60 and the land 59 and out of the notch 63 in the spring 60 in readiness for sewing. The spring finger 64 in the notch 65 of the bobbin case lip 66 prevents the bobbin thread from being drawn beyond the land 59.

The manufacture of the rotary hook of this invention is facilitated by the above described construction particularly in view of the fact that only the throat 39 of the loop taker body contacts the needle thread during stitch formation. The hook beak ring 41 made as a separate element from the hook body may be hardened and finished by separate operations not influencing those necessary for the manufacture of the hook body. Moreover, the spaced bearing lugs 36 of the hook body provide a jam free bearing raceway for the bobbin case bearing rib 54.

In the assembly of the rotary hook after the hook body portion 32 is fastened by the screws 31 to the loop taker shaft 26, the rotation restraining plate 27 and bobbin case 34 are inserted and the hook beak ring is snapped in place completing the assembly.

The manner in which the loop taker of this invention manipulates thread during stitch formation is illustrated in FIGS. 5, 6, 6A, and 7.

FIG. 5 illustrates the position of parts as the loop taker beak 45 carries the seized needle thread loop about the bobbin case 37. It will be seen in FIG. 5 that the supply limb N of the needle thread loop, i.e., that which extends to the sewing machine take-up and the supply spool (not shown), will be engaged against the shoulder 56 on the bobbin ease bearing rib 54 while the work limb N of the needle thread loop, i.e., that which extends to the previous stitch, will be carried across the top of the loop taker beak ring 41 of the loop taker. FIG. 5 also illustrates the action upon both the needle and bobbin thread B of the thread camming fin 46 on the loop taker beak ring 41. Since the fin 46 extends radially inwardly over the bobbin case in a plane perpendicular to the loop taker axis, the fin will form a bight in the supply limb of needle thread between the shoulder 56 and the needle and will also form a bight in the bobbin thread B between the thread guide notch 63 and the work being stitched. The fin 46 thus provides a metering pull-off action upon the bobbin thread relieving the needle thread at stitch setting of this function thus providing for a more consistent stitch setting. The fin 46 also pulls down an increment of the supply limb of needle thread immediately prior to cast over, i.e., the point at which the needle thread loop is carried across the widest part of the loop taker, thus obviating undo tightness and tension in the needle thread loop at the point of maximum expansion by the loop taker.

FIG. 6 illustrates the position of parts as the needle thread loop progresses beyond cast over. The supply limb of needle thread will be shifted by the lead of the thread into the rotation restraining notch 75 beneath the bobbin case. As shown in FIG. 6A, the supply limb will be stopped by the interengagement of the rotation restraining finger 76 against the side of the notch 75.

FIG. 7 illustrates the position of parts as the needle thread loop is drawn up by the sewing machine take up with the needle thread loop being drawn off and ahead of the loop taker beak 45. As shown in FIG. 7, the supply limb of the needle thread loop remains constrained by the rotation restraining finger 76 in a manner which advantageously holds the diminishing needle thread loop in front of the needle path and presents erratic uncontrolled disposition of the thread loop. The arrangement of the thread pull-off fin 46 over to the bobbin case in a plane perpendicular to the axis of the loop taker, which is made possible by the bobbin case rotation restraint 75, 76 beneath the bobbin case and within the loop taker body 32, makes it possible to arrange the vertical axis rotary hook closely beneath the throat plate 16 as illustrated in FIG. 2.

The novel bobbin case rotation restraint provided by this invention also provides for selective positioning of the bobbin thread guiding notch 63 relatively to the path of needle reciprocation. In the position of parts illustrated in FIG. 1 the bobbin thread guiding notch 63 is arranged to one side of the path of needle reciprocation, thus favoring a consistent interconcatenation of bobbin and needle threads in the resulting stitches and minimizing the occurrance of half hitches which occur should the needle descend on the opposite side of the bobbin thread. The position illustrated in FIG. 1 is thus ideal for the formation of straight stitches.

By manipulating the upstanding pin 81 opposite the indicia 88 depicting zigzag stitches, the thread guide notch 63 will be positioned substantially radially opposite the centermost path of needle reciprocation within the range of lateral needle positions during zigzag sewing. In this position of parts the most favorable balance is obtained as between zigzag stitches to the left and right of the center position. In zigzag stitching the occurrence of periodic half hitch stitches is not objectionably noticeable as it is in a line of straight stitches, whereas on the other hand inequality in the balanced formation of left and right hand stitches is readily noticeable in zigzag stitches.

Having thus set forth the nature of this invention, what is claimed herein is:

1. A loop taker for a sewing machine having a frame with a work supporting surface, and a thread carrying needle endwise reciprocable through said work supporting surface, said loop taker comprising a circularly movable loop taker body formed with a bobbin case accommodating cavity, a loop taker shaft secured to said loop taker body and formed with a lengthwise bore communicating with said bobbin case accommodating cavity, means journaling said loop taker shaft in said sewing machine casing, bearing race means carried by said loop taker body within said bobbin case accommodating cavity, and ineluding means formed on said loop taker body and projecting into said cavity to define an inner race, an annular ring detachable from said loop taker body and formed with a needle thread engaging beak, and means for securing said annular ring on said loop taker body in a position extending radially within said bobbin case accommodating cavity to define an outer race, a bobbin case disposed in said bobbin case accommodating cavity, bearing means on said bobbin case complemental to said hearing means carried by said loop taker body, a bobbin case rotation restraining member aranged in said bobbin case accommodating cavity between said loop taker body and said bobbin case, interengaging rotation restraining elements on said rotation restraining member and on said bobbin case, and support means for said rotation restraining member secured to said sewing machine casing and extending from said casing through said loop taker shaft bore to said rotation restraining member.

2. A loop taker for a sewing machine as set forth in claim 1 in which a thread pull-off fin is carried by said loop taker body substantially diametrically opposite said needle thread engaging beak, said thread pull-01f fin comprising a flat plate extending radially over said bobbin case accommodating cavity.

3. A loop taker for a sewing machine as set forth in claim 1 in which the needle thread engaging beak on said annular ring is formed at one extremity of a flange which is formed on said annular ring and extends radially over said bobbin case accommodating cavity.

4. A loop taker for a sewing machine as set forth in claim 2 in which said thread pull-01f fin is formed as a radially inward enlargement of the annular ring of which said needle thread engaging beak is formed.

5. A loop taker for a sewing machine as set forth in claim 4 in which said loop taker comprises a rotary hook with said loop taker shaft journaling means arranged to position the axis of rotation of said rotary hook substantially perpendicular to said work supporting surface of said sewing machine casing, and in which the flange on said annular ring formed with said needle thread engaging beak and with said thread pull-off fin is disposed substantially parallel to and beneath said work supporting surface of said sewing machine casing.

6. A loop taker for a sewing machine as set forth in claim 1 in which said bobbin case includes a thread guide means from which bobbin thread issues from said bobbin case, and in which said support means for said rotation restraining member is selectively positionable relatively to said sewing machine casing to constrain said bobbin case thread guide means in any one of a range of positions relatively to the path of reciprocation of said sewing machine needle.

7. A loop taker for a sewing machine as set forth in claim 6 in which said loop taker is journaled in said casing as on an axis substantially perpendicular to the work supporting surface of said sewing machine casing, and in which said selectively positionable support means for said rotation restraining member includes a position in which said thread guide means is constrained radially opposite the path of reciprocation of said sewing machine needle.

8. A loop taker for a sewing machine as set forth in claim 7 in which said support means for said rotation restraining member includes a rod secured to said rotation restraining member and journaled in said loop taker shaft bore, a rock arm secured to said rod beneath said loop taker shaft, an upstanding pin defining an operator influenced handle secured in said rock arm and extending alongside said loop taker body, and detent means effective between said support means and said sewing machine casing defining at least two different selectable positions of said support means relatively to said sewing machine casing.

References Cited UNITED STATES PATENTS 722,496 3/ 1903 Dimond et al 112-229 875,612 12/1907 Parkes 112--23O HERBERT F. ROSS, Primary Examiner. 

